Pancreatic and hepatocellular cancers have poor survival rates. Based on data from the prior funding cycle showing that the multi-kinase inhibitor sorafenib synergistically interacts with the histone deacetylase inhibitor (HDACI) vorinostat to activate CD95 and kill renal, hepatocellular and pancreatic cancer lines, Bayer and Merck have sponsored phase I trials that will start in 2009. We also have published data demonstrating that geldanamycins (17AAG, 17DMAG) + MEK1/2 inhibitors synergize to kill liver and pancreatic tumor cells via CD95 activation. Both drug combinations cause a novel form of CD95 activation which is obligate for cell killing, but whether these combinations utilize all of the same molecular mechanisms to activate CD95 is unknown. We hypothesize based on published and preliminary data that Ca2+-dependent ROS generation by combined HSP90 antagonist and MEK1/2 inhibitor exposure will represent a key signal for ceramide- dependent CD95 activation and cell killing. We hypothesize, based on published and preliminary data, that inhibition of the class III RTK, PDGFRb, will represent a key primary target for sorafenib in the regulation of CD95 toxicity and autophagy regulation. We hypothesize that HDACIs potentiate sorafenib toxicity, in part, because they increase as a secondary event expression of CD95 and/or FAS-L via NFkB activation. Thus: Specific Aim 1: To determine the molecular mechanisms by which geldanamycin + MEK1/2 inhibitor treatment activates CD95. Specific Aim 2: To determine the molecular mechanisms by which sorafenib and vorinostat treatment activates CD95. Specific Aim 3: To determine mechanistically the relative importance of promoting additional extrinsic or intrinsic pathway activation to enhance the lethality of sorafenib+vorinostat in vitro and in vivo. Our goal is to determine in precise molecular detail the mechanisms of action of these drug combinations upstream of CD95 to improve their future clinical application, and to progress our yet-to-be translated findings from the bench / vivarium, to the bedside. PUBLIC HEALTH RELEVANCE: Pancreatic cancer is diagnosed in ~ 37,000 patients per annum, with ~34,000 deaths and a 5 year survival rate of <5%. Hepatoma is diagnosed in ~19,000 patients per annum with ~17,000 deaths, with a 5 year survival of <10%. Thus, pancreatic and hepatocellular cancers have very poor survival rates. Based on our published data from the prior cycle of funding, combining the multi-kinase inhibitor sorafenib with the histone deacetylase inhibitor (HDACI) vorinostat that demonstrated synergistic toxicity effects in Renal CC, HCC and pancreatic lines, Bayer and Merck have sponsored phase I trials in RCC and HCC that will start during 2009. Our goal now is to determine in even greater detail the mechanisms of action of these drugs to improve their future clinical application e.g. rationally, combined with additional targeted agent(s). In parallel studies, we published that geldanamycins and MEK1/2 inhibitors also demonstrate synergistic toxicity effects in Renal CC, HCC and pancreatic lines. Thus the secondary goal of this proposal is to prove detailed mechanistic mode-of-action data to move geldanamycin+MEK1/2 inhibitor therapy from the bench / vivarium, to the bedside.